Rhino Vray black buckets

[maxcaulfield]

Hello, i'm facing this problem in the render of my scene..

 

i have random black buckets in the area around the window..

all this started when i added a texdirt map in the diffuse channel of my walls texture.

 

Also it happens when i have ambient occlusion enabled. It seems to be a problem related ti ambient occlusion or dirt effect..

 

If i disable ambient occlusion AND texdirt map then the render is fine. But in other scenes, i always used ambient occlusion and i never had this problem so it's something related to this scene.